1. Field of the Invention
The present invention relates to a method of manufacturing a radiation image conversion panel that can form a stimulable phosphor layer of a uniform thickness on a support by applying to the support a stimulable phosphor-containing coating solution that contains a stimulable phosphor. Further, the present invention relates to a radiation image conversion panel that is obtained by this method of manufacturing a radiation image conversion panel, which is of a uniform film thickness and whose quality and practical value are high.
2. Description of the Related Art
Recently, as a technique to be used in place of radiography, there have been proposed radiation image conversion methods, for example, in Japanese Patent Application Laid-Open (JP-A) No. 55-12145, Japanese Patent Application Publication: (JP-B) No. 4-44720, and the like. Such radiation image conversion methods use a radiation image conversion panel (an accumulative fluorescent sheet) that includes a layer containing a stimulable phosphor. In the methods, radiation that has passed through a subject or radiation that has been emitted from a subject is absorbed by the stimulable phosphor in the panel, and thereafter, the stimulable phosphor is excited in time sequence by an electromagnetic wave (excitation light) that is selected from visible rays and infrared rays, so that the radiation energy accumulated in the stimulable phosphor becomes fluorescent and is discharged. By reading the fluorescent light optically, electronic signals are obtained. Then, the obtained electric signals are made into images. With the above-described radiation image conversion panel, it becomes possible to obtain a radiation image (an image formed by radiation) that, as compared with a case in which the conventional radiography is employed, has a smaller amount of exposure, can be image-processed by a computer, and has a large amount of information.
The above-described radiation image conversion panel can be formed by applying a coating solution that contains a stimulable phosphor onto a support.
Conventionally, various types of application methods for applying a coating solution to a support (web) so as to form a layer have been proposed. However, many of these methods relate to application techniques using coating solutions having low viscosity or to high speed application techniques in which a coating solution is applied at a speed higher than 100 m/min and at a film thickness of less than 100 xcexcm.
However, the stimulable phosphor-containing coating solution that is used for manufacturing the radiation image conversion panel is a highly viscous coating solution that contains a stimulable phosphor in a high concentration as a solid component. Further, the conventionally known coating techniques described above are incapable of sufficiently coping with cases such as, as with the radiation image conversion panel, the film thickness of the coated film of the stimulable phosphor-containing coating solution that is applied needs to be 100 xcexcm or more and the stimulable phosphor-containing coating solution needs to be applied at relatively low speed.
As the method of applying the above-mentioned highly viscous stimulable phosphor-containing coating solution to a m support (web), there has been proposed a variety of methods such as the stimulable phosphor-containing coating solution being continuously applied to a support (web) by use of a doctor blade, as described in JP-B No. 4-44720, or the stimulable phosphor-containing coating solution being applied to a support by use of a roll coater, a knife coater, or the like.
The above-described coating methods allow stable coating when used for coating for short lengths of approximately several tens of meters. However, when used for long lengths of approximately from several hundreds to several thousands of meters, there have been problems such as unstable film thickness of the coated film of the stimulable phosphor-containing coating solution, non-uniformity of thickness of the stimulable phosphor layer within the same plane, generation of coating streaks, unstable taking-up of the coated panel due to accumulation of the stimulable phosphor-containing coating solution at the end portions, and the like.
Particularly when used for medical diagnoses, since a variation of density in an image becomes signal data used for a diagnosis, the sensitivity (stimulated emission amount) of the entire stimulable phosphor layer must be extremely uniform, having no dispersion within the same plane. Further, the thickness of the stimulable phosphor layer and the sensitivity (stimulated emission amount) of the entire stimulable phosphor layer are closely related.
Therefore, with the conventional application methods in which the film thickness of the coated film is non-uniform, not only is it not possible to improve productivity, but also, it is difficult to make uniform the film thickness of the entire stimulable phosphor layer that can accumulate radiation energy, in other words, to make the sensitivity (stimulated emission amount) of the entire phosphor surface uniform.
The present invention aims to solve the aforementioned conventional problems and to attain the following object. Namely, an object of the present invention is to provide a method of manufacturing a radiation image conversion panel with high produceability in which, even when a highly viscous stimulable phosphor-containing coating solution, which contains a stimulable phosphor as a solid component in a high concentration, is applied to a support such that the film thickness is 100 xcexcm or more, a uniform film thickness on the support is obtained, and to provide a radiation image conversion, panel that is obtained by the method of manufacturing a radiation image conversion panel, which conversion panel has a uniform film thickness and high quality and practical value.
The means for solving the above are as follows:
(1) a method of manufacturing a radiation image conversion panel in which a stimulable phosphor-containing coating solution, which contains at least a stimulable phosphor and a binder, is applied to a support by use of an extrusion coater such that the film thickness of a coated film of the stimulable phosphor-containing coating solution is 100 xcexcm or more;
(2) a method of manufacturing a radiation image conversion panel according to the (1), wherein the film thickness of the coated film of the stimulable phosphor-containing coating solution is from 200 to 1,000 xcexcm;
(3) a method of manufacturing a radiation image conversion panel according to the (1) or (2), wherein at least one of the support and the extrusion coater is moved and the speed of the movement is from 0.5 to 50 m/min;
(4) a method of manufacturing a radiation image conversion panel according to one of the (1) through (3), wherein the viscosity of the stimulable phosphor-containing coating solution is from 1 to 10 Paxc2x7s;
(5) a method of manufacturing a radiation image conversion panel according to one of the (1) through (4), wherein the stimulable phosphor-containing coating solution is applied such that a gap A (xcexcm) between a discharge opening at the tip of the extrusion coater and the support, and a film thickness B (xcexcm) of the coated film of the stimulable phosphor-containing coating solution satisfy the following relational expression;
0.75xc3x97B+100xe2x89xa7Axe2x89xa71.10xc3x97B130
(6) a method of manufacturing a radiation image conversion panel according to one of the (1) through (5), wherein the extrusion coater is disposed on a surface of a first plane, and the support is disposed on a roller whose axis is located parallel to a direction orthogonal to the direction in which the stimulable phosphor-containing coating solution is discharged in a second plane that is located above the discharge opening at the tip of the extrusion coater and parallel to the first plane, such that an angle formed by, on the one hand, the direction of the shortest distance between the tip discharge opening and the roller and, on the other hand, the second plane is from 0 to 30xc2x0;
(7) a method of manufacturing a radiation image conversion panel according to one of the (1) through (6), wherein the extrusion coater is disposed on a surface of a first plane, and the support is disposed on a roller whose axis is located parallel to a direction orthogonal to the direction in which the stimulable phosphor-containing coating solution is discharged in a second plane that is located above the discharge opening at the tip of the extrusion coater and parallel to the first plane, such that an angle formed by the direction in which the stimulable phosphor-containing coating solution is discharged and the second plane is from 5 to 60xc2x0;
(8) a radiation image conversion panel obtained by the method of manufacturing a radiation image conversion panel according to one of the (1) through (7).